The common cold is a viral infection of the lining of the nose, sinuses, throat, and large airways. Symptoms of the cold start 1 to 3 days after infection. Usually, the first symptom is discomfort in the nose or throat. Later, the person starts sneezing, has a runny nose, and feels mildly ill. Fever is not common, but a mild fever may develop at the beginning of the illness. At first, the secretions from the nose are watery and clear and can be annoyingly plentiful; eventually they become thicker, opaque, yellow-green, and less abundant. Many people also develop a cough. Symptoms usually disappear in 4 to 10 days, although a cough often lasts into the second week.
A person with a cold should stay warm and comfortable and try to avoid spreading the infection to others. Anyone with a fever or severe symptoms should rest at home. Drinking fluids and inhaling steam or mist from a vaporizer may help to keep secretions loose and easier to expel.
Several popular non-prescription remedies that help the symptoms of a cold are available. For example, decongestants help open clogged nasal passages, antihistamines help dry a runny nose, and cough syrups make coughing easier by thinning secretions or suppressing cough. These drugs are most often sold as combinations but can also be obtained individually.
The olfactory region comprises cilia that project downward from the olfactory epithelium into a layer of mucous, which is about 60 microns thick. This mucous layer is a lipid-rich secretion that bathes the surface of the receptors at the epithelium surface. The mucous layer is produced by the Bowman's glands, which reside in the olfactory epithelium.
The mucous lipids assist in transporting the odorant molecules, as only volatile materials that are soluble in the mucous can interact with the olfactory receptors and produce the signals that the human brain interprets as odour.
Each olfactory receptor neuron has 8-20 cilia that are whip-like extensions 30-200 microns in length. The olfactory cilia are the sites where molecular reception with the odorant occurs and sensory transduction (i.e., transmission) starts. The olfactory epithelium also contains another sensory system in the form of “Trigeminal Nerve Receptors”. Together with the olfactory receptor system localized in the olfactory bulb, the 5th cranial or trigeminal nerve provides a second set of nerve endings which are responsible for tactile, pressure, pain and temperature sensations in the areas of the mouth, eyes and nasal cavity.
A number of chemical trigeminal stimulants produce effects described as hot, cold, tingling or irritating. For example, leavo-menthol produces the trigeminal feeling of “cold” at moderate concentrations and “hot” at high concentrations in the nasal cavity. Similarly camphor, which possesses markedly more aroma than menthol, also produces the “cold” sensation via interaction with trigeminal receptors. [Eccles, 1994; Hensel, 1974; Ohloff, 1994]. Ohloff states, “About 70% of all odours are said to stimulate the trigeminal nerve endings although, in general, they may be several times less sensitive than olfactory receptors”. [Ohlofff 1994]
Popular treatments of the common cold include steamy hot bath water that contains small amounts of essential oils, providing warm, moist air to help open nasal and bronchial passages. Essential oils can also be used in many humidifiers or in a tissue scented with the oils.
While steam inhalation is considered to be an effective method of liquefying respiratory tract fluid, a point of dispute is the value of adding volatile aromatic drugs to the water vaporizer, for which there is no evidences of efficacy. [Boyd & Pearson, 1946; Boyd & Sheppard, 1968; Ohloff, 1994]. It can be reasonably argued that the major amount of any drug passively inhaled (by breathing air or vapors) remains in the nose or the oro-pharynx.
Essential oils are traditionally believed to be useful in the symptomatic treatment of nasal congestion and these compounds can be found in several popular remedies in use for many years. Nevertheless the effects of these substances on the nose had been studied very little.
An early study was done in 1927 on the effects of camphor, eucalyptus and menthol sprayed directly onto the nasal mucosa of dogs and humans, which concluded that these substances had no decongestant action but produced only a sensation of nasal patency. The Author suggested that this sensation could be the result of the action on temperature sensitive nerve endings. [Fox, 1927]
Another trial studied the effects of five minutes exposure to camphor, eucalyptus or menthol vapour on nasal resistance to airflow, assessed by rhinomanometry, and nasal sensation in 30 healthy volunteers. None of the essential oils had any significant effect on the nasal resistance (changes in nasal resistance between −10% and +10%), in contrast with 5 min exercise on the cycle ergometer, taken as a control, which produced about 80% reduction in nasal resistance. As far as the subjective impression is concerned, the majority of subjects reported a cold sensation on nasal inspiration. The Authors' conclusion was that “it therefore seems likely that the main property of camphor, eucalyptus and menthol is a stimulant action or sensitising effect on nasal cold receptors and this gives a sensation of increased airflow even though there may be no change in nasal resistance to airflow”.
The above results have been confirmed in a subsequent study, where the inspiratory and expiratory nasal resistance to airflow were measured in 35 healthy subjects after inhalation of a mixture of 125 mg menthol+50 mg camphor+10 mg oil of pine+5 mg methyl salicylate, without any effect on the resistance of the left nasal passage.
Eucalyptus was first used by Australian aborigines, who used the leaves as a remedy for fevers. In the 1800s, crew members of an Australian freighter developed high fevers, but were able to successfully cure their condition using Eucalyptus tea. Thus, Eucalyptus became well known throughout Europe and the Mediterranean as the Australian fever tree.
The essential oil in the leaves is commonly used for medicinal purposes. The essential oil from the fruit, buds, and branches contain from 15-60% of 1,8-cineole (eucalyptol). Activities attributed to this compound include: anaesthetic, antiseptic, expectorant, antitussive, counterirritant and sedative. Eucalyptus oil is said to function in a fashion similar to that of menthol by acting on receptors in the nasal mucosa, leading to a reduction in symptoms such as nasal congestion.
Camphor is a pungent white crystalline substance obtained from the Cimmamonurn camphora tree or made synthetically.
It is used in medicine as a stimulant, diaphoretic and inhalant. Camphor has been found beneficial in asthma and spasmodic cough and the powder may be used as a snuff for the relief of nervous headache and catarrh. It has found use as a 1% solution against catarrhal disease, both acute and chronic. Good results have likewise being reported from its use in sore throat and acute bronchitis.
Menthol is a compound obtained from peppermint oil or other mint oils or made synthetically. Menthol has local anaesthetic and counterirritant qualities, and has the following chemical structure:

Menthol induces cold sensations when applied to the skin and mucosal membranes, the underlying mechanism being a stimulating action on peripheral cold receptors. This stimulation of cold receptors is independent of any change in temperature. Cold receptor activity is proposed to be controlled by a calcium stimulated outward current. It is hypothesized that menthol induces a calcium inactivation, preventing the efflux of calcium from intracellular space, which loosen the control of this mechanism and increases the afferent activity of cold sensors. Calcium application completely abolishes the stimulating menthol effect on cold receptors. The coolant action of menthol has been extensively discussed by Eccles in 1994 who showed that the activation of cold receptors by calcium channel blocking activity resulted in cold sensation within the nose which produced the sensation of a free decongested nose. Therefore menthol probably selectively stimulates cold receptors by impeding calcium current.
Pinus sylvestris/Pumilius: Pine oil is extracted from the needles (pine needle oil) as well as twigs and buds (pine oil) of pine trees by steam distillation in yields of 0.1-0.5%. Constituents of pine oil include 50-97% monoterpene hydrocarbons, such as α-pinene, with lesser amounts of 3-carene, dipentene, β-pinen, D-limonene, α-terpinene, γ-terpinene, cis-β-ocimene, myrcene, camphene, sabinene, and terpinolene. The approved modern therapeutic applications for pine needle oil are based on its history of use in well established systems of traditional and conventional medicines, and on phytochemical investigations and pharmacological studies.
In Germany, pine needle oil is official in the German Pharmacopoeia, the Standard Licenses for Finished Drugs Monographs, and it is also approved by Commission E. Drops of the essential oil are added to boiling water for inhalation of steam vapor as a supportive treatment for catarrhal diseases of the respiratory tract. The drops are also applied topically by carefully rubbing into the skin for rheumatic complaints. In German pediatric medicine, Pumilio pine oil is used as a component of “Inhalatio composite” formulation (eucalyptus oil 45%, Pumilio pine oil 45%, peppermint oil 10%), intended especially for coryza (acute cold and nasal inflammation) and nasal catarrh in children. The Commission E reports secretolytic, hyperemic, and slight antiseptic activity.
Pine Oil: In the United States, pine needle oil, distilled from the leaves of dwarf pine, is official in the National Formulary. It is used as a component in cough and cold medicines, vaporizer fluids, nasal decongestants, and analgesic ointments. The essential oil of Scots pine (P. sylvestris) is also used in aromatherapy. Pumilius Essential Oil (extracted by Mountain Pine) contains a mix of triterpens hydrocarbouns like Alfa and Beta pinene, limonene, fellandrene, canfene and borneol, which have antiseptic and decongestant action. Given the volatility of these compounds, they have a high therapeutic action especially on breathing mechanisms.
Bitter orange (Citrus aurantium) oil is extracted from the bitter orange flower and peel and used to treat sore throat. This essential oil has a euphoric, invigorating, cooling and balancing effect on the mind. On the physical side, it is an antispasmodic, antiseptic, disinfectant and anti fever agent. In the natural tradition it is use as a remedy for cough and cold.
Lavender: The volatile essential oil of lavender contains many constituents, including perillyl alcohol and linalool. The oil is thought to be calming and thus can be helpful in some cases of insomnia. One trial of elderly people with sleeping troubles found that inhaling lavender oil was as effective as some commonly prescribed sleep medications. A large clinical trial found that lavender oil added to a bath was no more effective than a placebo for relieving perineal discomfort immediately after childbirth. However, perineal pain was reduced three to five days afterward.
Lavender is recommended by the German Commission E monograph for indigestion and nervous intestinal discomfort. The German Commission E monograph suggests 1-2 teaspoons (5-10 grams) of the herb be taken as a tea. For internal applications, ½-¾ teaspoon (2-4 ml) of tincture can be taken two or three times per day. Several drops of the oil can be added to a bath or diluted in vegetable oil for topical applications. The concentrated oil is not for internal use, except under medical supervision.